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buffer: optimize hex_decode · nodejs/node@4158272 · GitHub

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Commit 4158272

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chjj
authored and
evanlucas
committed
buffer: optimize hex_decode
PR-URL: #7602 Reviewed-By: Anna Henningsen <anna@addaleax.net>
1 parent 0858e62 commit 4158272

3 files changed

Lines changed: 93 additions & 13 deletions

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‎benchmark/buffers/buffer-hex.js‎

Lines changed: 26 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,26 @@
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'use strict';
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const common = require('../common.js');
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const bench = common.createBenchmark(main, {
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len: [0, 1, 64, 1024],
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n: [1e7]
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});
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function main(conf) {
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const len = conf.len | 0;
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const n = conf.n | 0;
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const buf = Buffer.alloc(len);
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for (let i = 0; i < buf.length; i++)
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buf[i] = i & 0xff;
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const hex = buf.toString('hex');
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bench.start();
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for (let i = 0; i < n; i += 1)
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Buffer.from(hex, 'hex');
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bench.end(n);
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}

‎src/string_bytes.cc‎

Lines changed: 24 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -143,16 +143,27 @@ const int8_t unbase64_table[256] =
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};
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145145

146-
template <typename TypeName>
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unsigned hex2bin(TypeName c) {
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if (c >= '0' && c <= '9')
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return c - '0';
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if (c >= 'A' && c <= 'F')
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return 10 + (c - 'A');
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if (c >= 'a' && c <= 'f')
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return 10 + (c - 'a');
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return static_cast<unsigned>(-1);
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}
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static const int8_t unhex_table[256] =
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{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -1, -1, -1, -1, -1, -1,
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-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
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-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
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};
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#define unhex(x) \
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static_cast<unsigned>(unhex_table[static_cast<uint8_t>(x)])
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157168

158169
template <typename TypeName>
@@ -162,11 +173,11 @@ size_t hex_decode(char* buf,
162173
const size_t srcLen) {
163174
size_t i;
164175
for (i = 0; i < len && i * 2 + 1 < srcLen; ++i) {
165-
unsigned a = hex2bin(src[i * 2 + 0]);
166-
unsigned b = hex2bin(src[i * 2 + 1]);
176+
unsigned a = unhex(src[i * 2 + 0]);
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unsigned b = unhex(src[i * 2 + 1]);
167178
if (!~a || !~b)
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return i;
169-
buf[i] = a * 16 + b;
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buf[i] = (a << 4) | b;
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}
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172183
return i;

‎test/parallel/test-buffer-badhex.js‎

Lines changed: 43 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,43 @@
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'use strict';
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require('../common');
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const assert = require('assert');
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const Buffer = require('buffer').Buffer;
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// Test hex strings and bad hex strings
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{
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const buf1 = Buffer.alloc(4);
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assert.strictEqual(buf1.length, 4);
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assert.deepStrictEqual(buf1, new Buffer([0, 0, 0, 0]));
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assert.strictEqual(buf1.write('abcdxx', 0, 'hex'), 2);
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assert.deepStrictEqual(buf1, new Buffer([0xab, 0xcd, 0x00, 0x00]));
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assert.strictEqual(buf1.toString('hex'), 'abcd0000');
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assert.strictEqual(buf1.write('abcdef01', 0, 'hex'), 4);
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assert.deepStrictEqual(buf1, new Buffer([0xab, 0xcd, 0xef, 0x01]));
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assert.strictEqual(buf1.toString('hex'), 'abcdef01');
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const buf2 = Buffer.from(buf1.toString('hex'), 'hex');
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assert.strictEqual(buf1.toString('hex'), buf2.toString('hex'));
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const buf3 = Buffer.alloc(5);
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assert.strictEqual(buf3.write('abcdxx', 1, 'hex'), 2);
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assert.strictEqual(buf3.toString('hex'), '00abcd0000');
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const buf4 = Buffer.alloc(4);
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assert.deepStrictEqual(buf4, new Buffer([0, 0, 0, 0]));
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assert.strictEqual(buf4.write('xxabcd', 0, 'hex'), 0);
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assert.deepStrictEqual(buf4, new Buffer([0, 0, 0, 0]));
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assert.strictEqual(buf4.write('xxab', 1, 'hex'), 0);
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assert.deepStrictEqual(buf4, new Buffer([0, 0, 0, 0]));
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assert.strictEqual(buf4.write('cdxxab', 0, 'hex'), 1);
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assert.deepStrictEqual(buf4, new Buffer([0xcd, 0, 0, 0]));
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const buf5 = Buffer.alloc(256);
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for (let i = 0; i < 256; i++)
36+
buf5[i] = i;
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const hex = buf5.toString('hex');
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assert.deepStrictEqual(Buffer.from(hex, 'hex'), buf5);
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const badHex = hex.slice(0, 256) + 'xx' + hex.slice(256, 510);
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assert.deepStrictEqual(Buffer.from(badHex, 'hex'), buf5.slice(0, 128));
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}

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